Introduce MultiCIDRRangeAllocator

MultiCIDRRangeAllocator is a new Range Allocator which makes using
multiple ClusterCIDRs possible. It consists of two controllers, one for
reconciling the ClusterCIDR API objects and the other for allocating
Pod CIDRs to the nodes.

The allocation is based on the rules defined in
https://github.com/kubernetes/enhancements/tree/master/keps/sig-network/2593-multiple-cluster-cidrs

pkg/controller/nodeipam/ipam/range_allocator.go

@@ -41,13 +41,6 @@ import (
 	controllerutil "k8s.io/kubernetes/pkg/controller/util/node"
 )
 
-// cidrs are reserved, then node resource is patched with them
-// this type holds the reservation info for a node
-type nodeReservedCIDRs struct {
-	allocatedCIDRs []*net.IPNet
-	nodeName       string
-}
-
 type rangeAllocator struct {
 	client clientset.Interface
 	// cluster cidrs as passed in during controller creation
@@ -333,7 +326,7 @@ func (r *rangeAllocator) updateCIDRsAllocation(data nodeReservedCIDRs) error {
 	var err error
 	var node *v1.Node
 	defer r.removeNodeFromProcessing(data.nodeName)
-	cidrsString := cidrsAsString(data.allocatedCIDRs)
+	cidrsString := ipnetToStringList(data.allocatedCIDRs)
 	node, err = r.nodeLister.Get(data.nodeName)
 	if err != nil {
 		klog.Errorf("Failed while getting node %v for updating Node.Spec.PodCIDRs: %v", data.nodeName, err)
@@ -391,12 +384,3 @@ func (r *rangeAllocator) updateCIDRsAllocation(data nodeReservedCIDRs) error {
 	}
 	return err
 }
-
-// converts a slice of cidrs into <c-1>,<c-2>,<c-n>
-func cidrsAsString(inCIDRs []*net.IPNet) []string {
-	outCIDRs := make([]string, len(inCIDRs))
-	for idx, inCIDR := range inCIDRs {
-		outCIDRs[idx] = inCIDR.String()
-	}
-	return outCIDRs
-}